Holding units for stay in place molds

ABSTRACT

The instant invention provides stay in place molds for the construction of concrete structures comprising fiber cement panels held together by a series of holding units that are fastened only to the interior surfaces of the cement panels by fastening means that are kept inside of the width of said panels. The holding units are selectively distributed at the internal surfaces of the cement panels in a series of columns separated from each other at predetermined distance. Within each column each holding unit are apart form the next one at a predetermined distance. The particular structure of the holding units, particularly its small size and its distribution pattern at the interior surface of the molds facilitates the uniform contact of the liquid cement mixture and increases the strength and resistance of the structure prepared using the molds.

This application claims priority under 35 USC 120 to U.S. patent application Ser. No. 12/633,416 filed on Dec. 8, 2009.

TECHNICAL FIELD OF THE INVENTION

This invention relates to holding units useful in stay in place molds for the construction of concrete structures. More particularly, the invention is directed to holding units able to provide stay in place molds which are useful in the construction of monolithic concrete structures of excellent strength.

BACKGROUND OF THE INVENTION

Fiber cement panels, also known as fiber cement boards have been used in the elaboration of stay in place molds useful in the construction of concrete structures. In general terms, two fiber cement panels are vertically positioned and held together in order to create an internal cavity intended to be filled with liquid concrete mixture at the construction site.

The real challenge in the manufacture and use of said molds is to maintain both fiber cement panels held together firmly and to obtain a highly internal pressure resistance at the internal cavity of the form.

In most instances, said fiber cement panels hare held together by means of vertical and horizontal structural components which are attached internally or externally to the said panels, debilitating the whole structure. Said external components complicate the construction process, requiring external supports in order to counteract or balance the internal pressure created once the liquid cement mixture is poured inside the mold. Similarly, said external components difficult the alignment and proper connection of individual molds, as required in the formation of larger structures.

On the other hand, the use of complicated components assembled through the width of the fiber boards and passing along its internal cavity compromise the firmness and stability of the mold and the strength of the structure constructed with said mold. Internally, said structures occupy a large area of the internal cavity and thus, represents an obstruction that avoid the uniform contact of the liquid concrete mixture, which results in the formation of a non-monolithic, weak concrete structure. Externally, once the concrete structure is made, it is required to eliminate the external section of such components, which means additional work that can negatively affect the interior of the constructed structure.

Thus there is a need of stay in place fiber cement molds comprising holding units or spacer elements, easy to manage, friendly to insert mechanical and electrical construction features and particularly designed to increase the stability of the mold, capable of allow a uniform dispersion of internal pressure of the liquid mixture and to allow the uniform contact of the liquid cement mixture in order to provide concrete structures with excellent strength and resistance.

OBJECTS AND SUMMARY OF THE INVENTION

It is an object of the invention to provide stay in place fiber cement molds capable of holding the fiber cement boards with strong firmness, wherein the holding units are distributed exclusively in small areas of the internal cavity and without having any of their components exposed at the exterior surfaces of the fiber cement boards. Another object of the invention is to provide molds comprising fiber cement boards having excellent resistance to the internal pressure created by the liquid cement mixture, thus capable to stand said internal pressure without the need of any external supports or components.

Yet another object of the invention is to provide a mold wherein the liquid cement mixture is uniformly spread inside its internal cavity, allowing said mixture to form strong monolithic structures. Still another object of the invention is to provide strong fiber cement molds that are able to be firmly interconnected to another mold in order to produce uniform and strong larges sizes concrete structures. Yet another object of the invention is to provide a mold capable of render concrete structures that resists high pressure and heavy weights. In an additional embodiment, another object of the instant invention is to provide a mold comprising fiber cement boards capable of incorporate insulating materials and without the need of disturb the interior of the constructed wall after the cement construction mixture is poured. In a still another object of the invention is to provide a stay in place mold having its exterior surface substantially flat, thus providing a concrete structure already having flat external surfaces. In yet another object of the invention is to provide a mold wherein distance and distribution of re bars may be easily predetermined and established as demanded by a given or particular construction code.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and additional features and characteristics of the embodiments of the present invention will become more apparent from the following detailed description considered with reference to the accompanying drawings, which are used herein in a manner of example only, and wherein:

FIG. 1 represents diverse views of the holding unit having a flat-shaped main body.

FIG. 2 represents a method of manufacturing the holding unit illustrated in FIG. 1.

FIG. 3 represents holding unit illustrated in FIG. 1 with the corresponding preferred dimensions when using in a fiber cement panels of 4 feet per 8 feet.

FIG. 4 illustrates mold embodiments using the holding unit illustrated in FIG. 1.

FIGS. 5 and 6 illustrate a method of manufacturing a mold requiring holding unit illustrated in FIG. 1.

FIGS. 7 and 8 illustrate a holding unit having a hollow cylindrical main body.

FIG. 9 illustrates holding unit shown in FIG. 7 with the corresponding preferred dimensions when using in a fiber cement panels of 4 feet per 8 feet.

FIG. 10 represents mold embodiments using holding unit illustrated in FIG. 7.

FIG. 11 illustrates a process of manufacturing a mold requiring holding unit illustrated in FIG. 7.

FIG. 12 illustrates a cross sectional view of one of the mold according to the invention as already installed in a concrete wall.

FIG. 13 illustrates the use of a mold according to the instant invention in the construction of a concrete wall requiring joining of molds.

DETAILED DESCRIPTION OF THE EMBODIMENTS

The following detailed description illustrates the invention by way of example and is not limited to the particular limitations presented herein as principles of the invention. This description is directed to enable one skilled in the art to make and use the invention by describing embodiments, adaptations, variations and alternatives of the invention. Potential variations of the limitations herein described are within the scope of the invention. Particularly, the size and shapes of the invention's elements illustrated in the discussion may be varied and still provide molds having different sizes or geometric shapes, that are within the scope of the instant invention.

In reference to the drawings, FIGS. 1 and 7 illustrate embodiments of the holding units 10 and 30, according to the invention respectively and particularly designed as spacer for the herein described stay in place molds. Particularly, FIG. 1 illustrates internal holding units 10. It comprises a continuous flat, rectangular main body 11, having an indentation 12, substantially at the middle of the upper section of the main body 11. Lateral edges 13 and 14 run alongside the left and right side of the main body 11 respectively and are located perpendicularly to such left and right lateral sides of main body 11, forming a 90 degrees angle. The lower end 15 of the internal holding unit 10 is also located perpendicularly oriented toward the lower side of main body 11. At the lower section of the lateral edges 13 and 14 there is an aperture 16 that provides entering of fastening means 17, when connecting holding unit 10 to the internal surfaces of fiber cements boards 20, as illustrated in FIG. 4A-4C.

Internal holding unit 10 may be made of strong, rigid material, preferably a suitable metal such as steel and even more preferably galvanized steel. It may be molded as a single unit or it may be made as illustrated in FIG. 2, wherein galvanized steel plate 18 is cut off at the middle in order to form indentation 12. Said indentation 12 is used as a support for horizontally positioned re-bars 66. Perforation at the lower left and right sides of plate 18 creates aperture 16. The internal holding unit 10 may be obtained after cutting off the lower left and right edges of plate 18 and bending the left, right and lower edges of the plate 18 extremes sides or edges in a 90 degrees angle with respect to the axis of the flat rectangular main body 11. The particular dimensions of the internal holding unit 10 may varied depending on different factors such as the size of the desired mold, the width of the structure to be constructed with the mold, the size of horizontal 66 and vertical 65 re-bars to be introduced in the mold, and other construction specifications dictated by particulars legal constructions codes. Thus, the herein disclosed molds are adaptable to different construction codes requirements.

In a preferred embodiment, when using fiber cement boards 20 with dimensions of a 4 feet×8 feet, the metal plate 18 may have a total length of 6 inches and 1.25 inches height. A particular plate 18 of such dimensions provides an internal holding unit 10 having a main body 11 length of 5 inches, an internal indentation 12 of 1.25 inches long and 0.50 inches in depth; a left and right sides 13 and 14, respectively having a length of 0.44 inches and a lower side 15 having a length of 0.25 inches.

Similarly, FIG. 7 illustrates internal holding unit 30. It comprises a hollow cylindrical main body 23 having left and right threaded sections 24 and 25 and a middle section 26. As illustrated in more detail in FIG. 8, said middle section 26 is defined by the two rings 27 and 28 that surround the circumference of said main body 23 and are permanently located equidistantly from substantially the center of the main body 23. Middle section 26 together with two rings 27 and 28 provides a suitable accommodation space for re-bars 66 at the interior of the mold. At each extreme ends of the left and right sections 24 and 25, main body 23 are threaded to a squared plate 29 via a threaded cylindrical nut 22. Said cylindrical nut 22 is permanently located at substantially the center of the squared plates 29, which is internally threaded while the external surface 19 of squared plate 29 is flat. Holding unit 30 may be fastened to the internal surfaces of fiber cement boards 20 by means of any suitable glue. Thus, after gluing, holding unit 30 held both fiber cement panels 20 only at the internal surface of said fiber cement panels 20, without any interaction of the holding unit 30 with the external surfaces of the fiber cement panels.

The internal holding unit 30 may be made of any suitable solid, rigid material, preferably metal or plastic and even more preferably plastic. It may be molded in a single piece or, alternatively, it may be obtained after assembling two different pieces: main body 23 and two squared plates 29, as illustrated in FIG. 8. Both said pieces may be molded independently and further assembled by threading the ends of main body 23 to cylindrical nut 22 on squared plates 29.

The particular dimensions of the internal holding unit 30 may varied depending on different factors such as the size of the desired mold, the width of the structure to be constructed with the mold, the size of horizontal 66 and vertical 65 re-bars to be introduced in the mold, and other construction specifications dictated by particulars legal constructions codes.

As illustrated in FIG. 9, in a preferred embodiment when using fiber cement boards 20, with dimensions of 4 feet per 8 feet, the main cylindrical body 23 may have a length of 5.50 inches and an internal diameter of 0.5 inches; the plates 29 may have 0.125 inches thickness and 5×5 inches length with a cylindrical nut 22 of 0.5 inches in length, thus providing a holding unit 30 with a total length of 5 inches.

Among the main functions of the holding units 10 and 30 are holding the fiber cement panels 20 parallel to each other; providing excellent structural strength inside the molds capable to withstand extreme internal pressures created by the concrete mixture until it solidifies. Additionally, said holding units 10 and 30 provide support to horizontal re-bars 66 as required by any given particular structural specification and since each holding unit are connected only to the internal surface of the fiber cement panels 20, they provide stay in place molds having a flat external surface ready for painting once a concrete structure is constructed. Each holding unit 10 and 30 has a different physical structure and has been created exclusively to render concrete molds having extreme resistance to the internal pressure produce by liquid concrete mixture. Furthermore, holding units 10 and 30 are assembled at the internal cavity 32 of molds in a disperse pattern that uses only near 2 percent of the internal cavity of a mold. Therefore, near 98 percent of the concrete mixture is allow to be in direct contact with itself, which produces an extremely strong concrete structures, capable to resist the weight of additional structures above them, thus allowing the construction of high concrete structures such as buildings. Furthermore, the dispersion pattern of the holding units 10 and 30 and the small thickness of said holding units allows an accommodation of vertical re-bars 65 at a given distance specified by the structural design of the construction; in such a manner that the installation of electrical or mechanical features inside the mold is free of any interferences with said holding units. Similarly, the strength of the resulting walls is much more resistance to earth quake motions and similar external forces, thus increasing the security of said constructions and its inhabitants. Besides, the use of holding units 10 and 30 having a thin main body, allows the incorporation of internal reinforcements, if necessary or desired, thus increasing the versatility of the herein disclosed molds.

The internal holding unit 10 is useful in the manufacture of stay in place construction mold embodiments 7, 8 and 9 as illustrated in FIG. 4A though 4C, wherein the upper front sections of the molds have been cut off in order to illustrate the internal components of each embodiment. Each mold embodiments 7, 8 and 9 comprises two fiber cement panels 20, positioned parallel one to the other wherein each fiber cement panel 20 has a flat substantially uniform external surface. The holding units 10 are permanently fastened at the interior cavity 32 of the mold in pattern of a series of multiple columns. Each of said columns are apart from the next one at a predetermined distance. Similarly, each holding unit 10 within a given column is also apart from the next holding unit 10 at a predetermined distance.

The interior section of the mold may include an insulated foam panel 21, having the same dimensions of the fiber cement panels 20. Said optional foam panel 21 may serves as an insulating element and is attached to the internal surface of one of the fiber cement panels 20. Embodiment 7, in FIG. 4A has its lateral sides free and open. Embodiment 8 however, comprises two interconnecting units 31, which are located along the left edges of the internal section of fiber cements boards 20. Fiber cement boards 20, and foam panel 21 are commercially available. Interconnecting units 31 are made of a fiber cement panel 20 that has been cut off at a suitable size. Said interconnection units 31 allow the joining of individual molds in order to constructs larger size walls, as further explained below. Similarly, each mold embodiment 7, 8 and 9 also comprises multiple internal holding units 10, which are distributed in a particular arrangement over the internal surface of fiber cement boards 20. The extremes or ends of each internal holding unit are physically connected only to the internal surfaces of the fiber cement panels 20, thus creating an internal cavity 32.

On the other hand, mold embodiment 9 as illustrated in FIG. 4C has a closing unit 33 enclosing the internal cavity 32 of the mold 9. Said closing unit 33 may be made of fiber cement panel that has been cut off at the convenient size in order to close the internal cavity 32 of the mold 9. Said closing unit 33 may be installed once the mold is already installed at the construction site and previous to fill the internal cavity 32 of the mold 9 with liquid concrete mixture.

The manufacture of the mold embodiments illustrated FIG. 4 is shown in FIG. 5, wherein the initial step is the proper setting of the fiber cement boards 20. Said setting requires a series of perforations in a particular size or shapes and further distributed in a particular pattern of columns (verticals) and rows (horizontal) at a predetermined distance and within a particular surface area of the fiber cement panels 20. Said arrangement is aimed to achieve the maximum strength and resistance of the resulted mold, which must be within the limits established by a given construction code and to properly organize the required horizontally oriented re-bars 66. For instance, as illustrated in FIG. 5A and FIG. 5B, the distance between a given perforation 34 and the following perforation 35 within columns is dictated by the distance between a given horizontal re-bars 66 and the next horizontal re-bars 66 as required by any given construction specification. In the illustrated example such distance is illustrated as six inches.

FIGS. 5A-5D illustrate the initial preparation of a fiber cement panel 20 having particular dimensions of 4 feet per 8 feet; wherein the internal surface of the fiber cement panel 20 that eventually will contain the holding units 10 is delimitated by a left, right, top and bottom sections of a predetermined size of three inches. In the illustrated example, the top and bottom distance is three inches, while the left and right margins are of four inches. Said margins are free of perforations and frame the internal area of the fiber cement panel 20 containing the perforations aligned in columns and rows pattern that will be fastened to the holding unit 10.

Regarding the dimensions of the perforations itself, as shown in FIG. 5C, each perforation 40 comprises a first drill or opening 41 and a second opening 42, which is at substantially the center of opening 41. The first opening 41 has a larger diameter than second opening 42. In a preferred embodiment, first opening 41 has a diameter of 0.75 inches and a depth of 0.12 inches. On the other hand, the second opening 42 has a diameter of 0.187 inches and a length of 0.38 inches. Therefore, the width of the fiber cement board 20 is 0.5 inches; there is a remaining of 0.38 inches not affected by the initial opening 41. The second opening 42, at the center of the first opening 41, passes through the internal surface of the fiber cement board 20 is made with a 0.1875 inches ( 3/16) inches drill.

After the perforation of a first fiber cement panel 20, an identical perforation pattern is performed in the second fiber cement panel to be used in the same mold. Thus, a mold 7 comprising two fiber cement panels 20 with dimensions of 4 feet×8 feet and with the specifications requiring a six inches separation of horizontally oriented re-bars, there will be a total of 96 perforations on each panel.

Once the fiber cement panels 20 have been perforated, the optional insulating foam panel 21, if used, is also perforated, wherein the perforations of the foam panel 21 are located at the same position of the perforations of the fiber cement panels 20. However, the perforations on the foam panel 21 have a diameter corresponding to the lateral edge 14 of the holding unit 10, as illustrated in FIG. 5E.

After the perforations on the fiber cement panels 20 and the foam panel 21 are done, the mold is assembled by gluing foam panel 21 on the internal surface of the external board 20 and further fastening holding units 10 to each perforation on the internal surface of each one of the fiber cement boards 20, thus creating internal cavity 32. Said assembling is illustrated in FIG. 6A and 6 B. The fastening means used to fast or secure the holding unit 10 to the panels 20 may be any suitable fastening means, such as screws, bolts or rivets, and more particularly preferred is the use of flathead screws 17, having flathead 46 that perfectly fits on the first opening 41 and having a threaded section 47 that fits second opening 42. Once all the fastening means are properly fastened, the external sections of first opening 41 are plastered, thus providing mold 7 with a smooth, flat, finished external surface.

Optionally and depending of the construction needs, interconnecting units 31 may be connected to one of the lateral sides of the mold 7, if necessary, in order to provide a joining mechanism as shown in embodiment 8 illustrated in FIG. 4B, as may be required depending of the size of desired wall under construction.

FIG. 10 illustrates stay in place mold embodiments requiring holding unit 30, wherein the front section of said mold embodiments 48, 49 and 50 have been cut off in order to show its internal components. In a similar manner that the mold embodiments 7, 8 and 9, the mold embodiments 48, 49 and 50 comprise two fiber cement panels 20, positioned parallel one to the other, wherein each fiber cement panel 20 has a flat substantially uniform external surface and a series of holding units 30 at a predetermined position and permanently fastened to the internal surface of the fiber cement panels 20 in a pattern of a series of multiple columns, each of said column being apart from the others at a predetermined distance and each holding unit 30 within a column being apart from the next holding 30 unit at a is predetermined distance. The exterior section of the mold may include an insulated foam panel 21, having the same dimensions of the fiber cement panels. Said optional foam panel 21 serves as an insulating element and is attached to the internal surface of one of the fiber cement panels. Embodiment 48, in FIG. 10A has its lateral sides free and open. Embodiment 49 in FIG. 10 B, however comprises two interconnecting units 31, which are located along the left edges of the internal section of fiber cements boards 20. Fiber cement boards 20, and foam panels 21 are commercially available. Interconnecting units 31 are made of a fiber cement board 20 that has been cut off at a suitable size. Said interconnection units 31 allow the joining of individual molds in order to constructs larger size walls. Similarly, each mold embodiments also comprises multiple internal holding units 30, which are distributed in a particular arrangement over the internal surface of fiber cement boards 20. The extremes or ends of each internal holding unit 30 are physically connected to the internal surfaces of the fiber cement panels 20, thus creating an internal cavity 32.

On the other hand, embodiment 50 as illustrated in FIG. 10C has a closing unit 33 enclosing the internal cavity 32 of the mold 50. Said closing unit 33 may be made of fiber cement panel that has been cut off at the convenient size in order to close the internal cavity 32 of the mold 50. Said closing unit may be installed once the mold is already installed at the construction site and previous to fill the internal cavity 32 of the mold with liquid concrete mixture.

FIG. 11 illustrates the use of holding unit 22 in the manufacture of molds embodiments illustrated in FIG. 10. The initial step is the fastening of the holding unit 30 on the internal surfaces of fiber cement panels 20 by gluing the flat external surface 19 of squared plates 29 on a particular area of the internal surface of one the fiber cement panels 20, as shown in FIGS. 11A and 11 B. Following the same principles as established in the manufacture of embodiments illustrated in FIG. 5; the holding units 30 are fastened in a series of columns and rows at a predetermined distance dictated by the required distance between adjacent re-bars of a given construction code. Once the holding units 30 have been fastened to the first fiber cement panel 20, a perforated foam panel 21 as illustrated in FIG. 11 C, is inserted and glued to the interior surface of the fiber cement panel 20 containing the holding units 30, as shown in FIG. 11 D. The assembling is complete once the second fiber cement panel 20 is fastened to the external surface of the squared plates 29, as illustrated in FIG. 11 D.

In operational terms, the mold embodiments 7, 8, 9 and 48, 49 and 50 are used in the construction of concrete or cement walls, houses, buildings and similar structures. FIG. 12 illustrates the assembled of mold embodiment 7 to a given structure site, wherein dowel 52 on construction site 53 is attached to the vertical re-bar 65 and wherein horizontally oriented re-bars 66 are resting on indentations 12 of holding unit 10. Similarly, FIG. 13A-13C illustrate the joining of two mold embodiments 8 in the construction of a larger size wall 68 by means of interconnecting unit 31 and wherein the distribution and accommodation of vertical re-bars 65 and horizontal re-bars 66 inside the internal cavity 32 of mold embodiment 8 are shown.

While the invention has been described in conjunction with some embodiments, it is to be understood that many alternatives, modifications, and variations will be apparent to those skilled in the art in light of the forgoing description. Accordingly, the invention is intended to embrace all such alternatives, modifications and variations falling within the spirit and scope of the appended claims. 

1) A holding unit useful in holding two fiber cement units together, said holding unit comprising: a) a flat rectangular main body; b) an indentation substantially located at the center of the upper side of the flat rectangular main body; c) left and right lateral edges perpendicularly located at the lateral sides of the rectangular body, d) an opening at the sides of each one of the lateral edges; e) a lower edge perpendicularly positioned at the lower side of the bottom side of the flat rectangular main body and; wherein said main body, lateral edges and lower edges are made of metal. 2) The holding unit of claim 1, wherein said metal is steel. 3) The holding unit of claim 2, wherein said steel is galvanized steel. 4) A stay in place construction mold useful in the construction of concrete walls, said mold comprising: (a) two fiber cement panels positioned parallel one to the other; each fiber cement panel having a flat substantially uniform external surface and an internal surface; (b) multiple holding units, said holding units comprising: a flat rectangular main body; an indentation substantially located at the center of the upper side of the flat rectangular main body; a left and right lateral edges perpendicularly located at the lateral sides of the rectangular body, an opening at the sides of each one of the lateral edges, a lower edge perpendicularly positioned at the lower side of the bottom side of the flat rectangular main body, wherein each of said holding units are fastened to the internal surface of the fiber cement panels in a series of multiple columns, each of said column being apart from the others at a predetermined distance and each holding unit within a column being apart from the next holding unit at a predetermined distance, d) fastening means for fastening said holding units and said internal surface of said fiber cement panels, wherein the fastening means are permanently connected to said holding units via the opening at the sides of each one of the lateral edges of the said holding units as well as permanently connected to the internal surface of the fiber cement panels only at the internal width section of each internal surface of the fiber cement panels. 5) The mold as recited in claim 4 further comprising a foam panel having the same dimensions of the fiber cement panels, being attached to the internal surface of one of the fiber cement panels. 6) The mold as recited in claim 4, further comprising two interconnecting fiber cement units connected at one of the lateral side of the mold. 7) The mold as recited in claim 4, further comprising the closing unit that enclosed the left and right ends of the mold. 8) The mold as recited in claim 4, wherein the fastening unit is selected from the group of as glue, bolts and rivets, screws or flathead screw. 9) The mold as recited in claim 8, wherein the fastening unit is a flathead screw. 10) The mold as recited in claim 4, wherein the holding units are made of metal. 11) The mold as recited in claim 10, wherein said metal is steel. 12) The mold as recited in claim 11, wherein said metal is galvanized steel. 13) A holding unit useful in holding two fiber cement units together, said holding unit comprising: a hollow cylindrical main body with threaded ends; two rings surrounding the circumference of said main body and permanently located equidistantly from substantially the center of the main body; two squared plates; a cylindrical nut permanently located at the center of the squared plates and; wherein the ends of the main body are threaded to the cylindrical nut of the squared plates. 14) The holding unit as recited in 13, wherein said holding unit is made of plastic or metal. 15) The holding unit as recited in 14, wherein said holding unit is made of plastic. 16) The holding unit as recited in 13, wherein the two squared plates are detachable from the main body. 17) A stay in place construction mold useful in the construction of concrete walls, said mold comprising: a) two fiber cement panels positioned parallel one to the other; each fiber cement panel having a substantially flat external surface and an internal surface; b) multiple holding units, said holding units comprising: a hollow cylindrical main body with threaded ends; two rings surrounding the circumference of said main body and permanently located equidistantly from substantially the center of the main body; two squared plates; a cylindrical nut permanently located at the center of the squared plates and; wherein the ends of the main body are threaded to the cylindrical nut of the squared plates and; wherein the external surface of said squared plates are glued at the internal surfaces of the fiber cement panels creating a series of multiple columns, wherein each column is apart from the next one at a predetermined distance and wherein each holding unit is separated from the next holding unit within a given column at a predetermined distance. 18) The mold as recited in claim 17, further comprising a foam panel having the same dimensions of the fiber cement panels and attached to the internal surface of one of the fiber cement panels. 19) The mold as recited in claim 17, further comprising interconnecting fiber cement units connected at one of the lateral sides of the mold. 20) The mold as recited in claim 17, further comprising closing units that enclosed the left and right ends of the mold. 